1. Field of the Invention
The present invention generally relates to a face image processing system including a means for setting an eye detecting region on the basis of a naris reference position by resorting to an image processing. More specifically, the invention is concerned with a method of detecting a naris or nares and a naris reference position.
2. Description of Related Art
For having better understanding of the invention, background techniques thereof will first be described in some detail. As the eye detecting region setting means known heretofore, there may be mentioned a system disclosed, for example, in Japanese Unexamined Patent Application Publication No. 227278/1994 (JP-A-6-227278). FIG. 18 is a block diagram showing a generally a configuration of a whole system including an eyeball existing region setting means 47.
Referring to FIG. 18, setting of an eyeball existing region by an eyeball existing region setting means 47 is effected within an face image 49 illustrated in FIG. 19 and obtained through a binarization processing executed by a binarizing means 48. More specifically, the eyeball existing region setting means 47 sets at first a search starting line 50 at a frame center within the binarized image, as shown in FIG. 19. Starting from the search starting line 50, the number of white pixels existing continuously is counted leftwards and rightwards, respectively, whereon a leftmost x-coordinate (XLM) 51 and a rightmost x-coordinate (XRM) 52 are stored which correspond to the maximum counts in the left and right directions, respectively. On the basis of the leftmost and rightmost coordinates, transverse widths of the eyeball existing regions are established in accordance with the following expressions: EQU center coordinate of abscissa=XC=XLM+((XRM-XLM)/2) EQU leftmost x-coordinate 53L of a left-eye window=X1=XLM EQU rightmost x-coordinate 53R of a left-eye window=X2=XC-25 EQU leftmost x-coordinate 54L of a right-eye window=XX1=XC+25 EQU rightmost x-coordinate 54R of a right-eye window=XX2=XRM
Subsequently, longitudinal or vertical widths of the eyeball existing regions are established in such a manner as described below.
For the left eye as viewed in the figure, the starting point is set at a position (X2-10) shifted by 10 dots from the right x-coordinate X2 of the left-eye window and a search range is set between the points (X2-10) and (X2-90) in order to evade the detection of black areas corresponding to naris, as can be seen from FIGS. 20A and 20B. A search starting line 55 (YL) is set between the scanning line having the left and right ends determined, whereon the scanning is performed in the horizontal or transverse direction periodically at an interval of four dots from the line YL to 0 in the vertical direction to thereby determine the bottom points (maximum y-coordinate points: BY1MAX and BY2MAX) of the first and second black regions as counted from the scan starting point and decides presence or absence of the spectacles. The y-coordinates determining the longitudinal or vertical width of the eyeball existing region can be given by the following expressions:
&lt;without spectacles&gt; EQU top y-coordinate of the eye window=YT=BY1MAX-40 EQU bottom y-coordinate of the eye window=YB=BY1MAX+10 PA1 &lt;with spectacles&gt; EQU top y-coordinate of the eye window=YT=BY2MAX-40 EQU bottom y-coordinate of the eye window=YB=BY2MAX+10
Similarly, for the right-hand eye, the bottom points of the first and second black regions from the scan starting point are determined by scanning periodically at an interval of four dots in the transverse or horizontal direction and the presence or absence of the spectacles is determined, whereon the top and bottom coordinates of the right eye is established through the similar procedure as in the case of the left eye. FIG. 21 is a view showing an eye window 56 set up through the procedure described above.
In conjunction with the conventional face image processing system described above, it is noted that the binarized region of the image tends to change or vary in dependence on weather, orientation of the face and other factors. Thus, the binarized region is unstable. However, for the eyeball existing region setting means 47 described above, it is required that the face contour position and/or the black regions such as those corresponding to the eyes, eyebrows and others have to be detected with high accuracy for setting the frame widths. Such detection may become difficult in dependence on the binarized states, possibly leading to setting of an erroneous eyeball existing region, giving rise to a problem.